Synthesis and Structure-Activity Relationship Studies of N-monosubstituted Aroylthioureas as Urease Inhibitors.

BACKGROUND

Thiourea is a classical urease inhibitor which is usually used as a positive control, and many N,N'-disubstituted thioureas have been determined as urease inhibitors. However, due to steric hindrance, N,N'-disubstituted thiourea motif could not bind urease as thiourea. On the contrary, N-monosubstituted thiourea with a tiny thiourea motif could theoretically bind into the active pocket as thiourea.

OBJECTIVE

A series of N-monosubstituted aroylthioureas were designed and synthesized for evaluation as urease inhibitors.

METHODS

Urease inhibition was determined by the indophenol method and IC values were calculated using computerized linear regression analysis of quantal log dose-probit functions. The kinetic parameters were estimated via surface plasmon resonance (SPR) and by nonlinear regression analysis based on the mixed type inhibition model derived from Michaelis-Menten kinetics.

RESULTS

Compounds b2, b11, and b19 reversibly inhibited urease with a mixed mechanism, and showed excellent potency against both cell-free urease and urease in the intact cell, with IC values being 90- to 450-fold and 5- to 50-fold lower than the positive control acetohydroxamic acid, respectively. The most potent compound b11 showed an IC value of 0.060 ± 0.004μM against cell-free urease, which bound to urea binding site with a very low KD value (0.420±0.003nM) and a very long residence time (6.7 min). Compound b11 was also demonstrated to have very low cytotoxicity to mammalian cells.

CONCLUSION

The results revealed that N-monosubstituted aroylthioureas bound to the active site of urease as expected, and represent a new class of urease inhibitors for the development of potential therapeutics against infections caused by urease-containing pathogens.